1. Field of the Invention
This invention relates to solid-state electrochemical devices capable of transporting ions through an electrolyte. Specifically, this invention relates to apparatus for the transport of ions through series tubular structures having improved electrical and pneumatic integrity.
2. Statement of the Art
Conductive solids which transport ions, such as oxygen ions, are known in the art and are useful in many applications, including fuel cells, gas production and separation/purification, and gas sensing or monitoring. In certain applications, a series of tubular electrolytic cells joined together provide increased electrochemical operation. An example of a series tubular system used as a fuel cell is disclosed in U.S. Pat. No. 4,431,715 to Isenberg, issued Feb. 14, 1984.
Efficient operation of series tubular cells has been compromised in prior art systems by inherent weaknesses in system design and configuration. For example, individual electrolytic cells are joined together by means generally known as an interconnect, which seals the tubes together and provides an electrical connection therebetween. However, prior art interconnects often fail because of degradation of the seal. The high temperatures at which electrolytic cells operate cause corrosion between the electrical conductor and the seal of the interconnect and sealing integrity is lost.
In addition, it has been difficult to produce an effective seal for use with high efficiency electrolytes or electrodes because of high operating temperature conditions. That is, when using silver or silver alloy based electrodes, for example, the maximum temperature of the sealing material is limited to the melting point of silver or silver alloy. Yet, the glass must maintain sufficient viscosity at such high operation temperatures to retain a seal over sustained periods of time.
Further problems have been experienced in prior art series tubular cells due to limitations experienced in configuring multiple cells in an efficient manner. With prior art systems, the interconnects limit the amount of manifolding which can be done with the tubes. The prior art interconnects currently used do not allow variation in configuration and manifolding because of a loss in pneumatic integrity of such systems.
Thus, it would be an improvement in the art to provide a series tubular electrochemical system having improved interconnects between the tubes to assure electrical and pneumatic integrity of the system and to provide sealing integrity between the tubes. It would be a further improvement in the art to provide a series tubular electrolytic cell system which provides simple interconnection of the tubes while permitting variation in manifolding and configuration.